Selecting correct prop for boat.

[denpat]

I have a 2010 Alumacraft Dominator 175 Sport with a 2010 Mercury Optimax 125 hp with full windshield that I am trying to find the correct prop to make it perform correctly. I have a full tank of gas, 38 gallon, all fishing equipment and two people in the boat. I am at 5000 feet altitude and the temperature was 70 degress. Slight chop on the water and only a slight breeze. The motor has an Mercury black diamond aluminum 15 pitch prop. At WOT I hit the rev limiter so I couldn't get a high end rpm. I replaced the 15 pitch with the same prop in 17 pitch and here is the results.

RPM was 5200
MPH was 35

600 RPM swing on 2" pitch change seem like a little much.

The rpm range on this motor is 5000 to 5750. I would like to get the rpm up a little and get the mgh to 40. Do you think I can do this with a 16 pitch prop so should I use a different prop with more cupping or go to a stainless steel.

Your help will be appreciated.

Denpat

 

[steelespike]

Re: Selecting correct prop for boat.

While 600 rpm is a bit much as you said; the rule of thumb is approximate and obviously many things enter into the final results. Yes I believe you could get 40 mph.
Unfortunately I'm not able to help much with a ss application.Your reduction in rpm could be from more cupping than you need and a few times here I have seen a reduction in cup do amazing things.Hopefully someone here will stop by with more information.You might read the description of the Black Diamond.